The first book in the Matthew Scudder series.
Prior to this first book, Scudder had been a married with kids decorated police officer (detective) for fifteen years. One night, while in a bar, Scudder stopped a robbery attempt. Unfortunately, one of his bullets hit a seven year old girl, and killed her. Scudder had retired from the police force immediately afterwards, even though he received a department commendation for the action. Scudder also is separated from his family (divorced from wife, barely sees the kids), and as much as possible, from the human race without becoming a hermit. All of this back-story occurred before this first book in the series, and Scudder has still not gotten over the death. Now Scudder does "favors" for people, though he stresses that he is not a licensed private investigator.
The book opens with a Mr. Cale Hanniford and Matthew Scudder in a bar. Hanniford wants to hire Scudder to investigate his daughter's life, though not necessarily her death. Mr. Hanniford had not had any real contact with his daughter Wendy over the past three years, and wants Scudder to fill in the details of her life. Mr. Hanniford isn't looking to find Wendy's killer, because the guy covered in blood found outside the apartment had already been caught, and had already committed suicide in jail (the roommate). Right around when Mr. Hanniford learned that his daughter was dead, the "killer" is caught and dies. He didn't have time to process his daughter dying, and get angry with the murderer. He just wants to find out about Wendy and her life. Scudder is aware of the case and agrees to look into Wendy's life.